This invention relates to a power steering apparatus mounted on various motor cars for decreasing steering force required for the driver.
In recent years, as steering apparatus of a motor car has been used power steering apparatus for the purpose of rapidly and smoothly steering the car, thus decreasing fatigue of the driver. According to such power steering device, an oil pump is driven by an internal combustion engine or an electric motor and the quantity of oil supplied to the power steering apparatus is controlled in accordance with the running conditions of the car so as to effect light and stable steering from a low speed running to a high speed running.
In such prior art power steering apparatus, however, the oil pump is constantly operated for the purpose of lightly operating the steering apparatus so that the power supplied to the oil pump is consumed in vain when the steering is not made. For this reason, as disclosed in German Laid Open Patent Specification No. 2,640,988, it has been proposed a method wherein the oil pump is operated only at the time of steering. With this method, however, each time the steering is made, the oil pump is operated so that even when the engine is stopped, steering causes the oil pump to operate whereby the battery mounted on the motor car would discharge excessively which often makes it difficult to start the engine.